<template>
	<view class="s-canvas">
		<canvas canvas-id="s-canvas" id="s-canvas"
			:style="{ width: contentWidth + 'px', height: contentHeight + 'px' }"></canvas>
	</view>
</template>
<script>
	export default {
		name: 'SIdentify',
		props: {
			identifyCode: {
				type: String,
				default: '1234'
			},
			fontSizeMin: {
				type: Number,
				default: 28
			},
			fontSizeMax: {
				type: Number,
				default: 30
			},
			backgroundColorMin: {
				type: Number,
				default: 180
			},
			backgroundColorMax: {
				type: Number,
				default: 240
			},
			colorMin: {
				type: Number,
				default: 50
			},
			colorMax: {
				type: Number,
				default: 160
			},
			lineColorMin: {
				type: Number,
				default: 40
			},
			lineColorMax: {
				type: Number,
				default: 180
			},
			dotColorMin: {
				type: Number,
				default: 0
			},
			dotColorMax: {
				type: Number,
				default: 255
			},
			contentWidth: {
				type: Number,
				default: 112
			},
			contentHeight: {
				type: Number,
				default: 38
			}
		},
		methods: {
			// 生成一个随机数
			randomNum(min, max) {
				return Math.floor(Math.random() * (max - min) + min)
			},
			// 生成一个随机的颜色
			randomColor(min, max) {
				var r = this.randomNum(min, max)
				var g = this.randomNum(min, max)
				var b = this.randomNum(min, max)
				return 'rgb(' + r + ',' + g + ',' + b + ')'
			},
			drawPic() {
				const ctx = uni.createCanvasContext('s-canvas', this)
				ctx.clearRect(0, 0, this.contentWidth, this.contentHeight)
				// 绘制背景
				ctx.fillStyle = this.randomColor(this.backgroundColorMin, this.backgroundColorMax)
				ctx.fillRect(0, 0, this.contentWidth, this.contentHeight)
				ctx.draw()
				// 绘制文字
				for (let i = 0; i < this.identifyCode.length; i++) {
					this.drawText(ctx, this.identifyCode[i], i)
				}
				// 绘制干扰线
				this.drawLine(ctx)
				// 绘制干扰点
				this.drawDot(ctx)
			},
			drawText(ctx, txt, i) {
				ctx.save() // 保存当前状态
				ctx.setFontSize(this.randomNum(this.fontSizeMin, this.fontSizeMax))
				ctx.font = 'SimHei'
				const x = (i + 1) * (this.contentWidth / (this.identifyCode.length + 1))
				const y = this.randomNum(this.fontSizeMax, this.contentHeight - 10)
				const deg = this.randomNum(-30, 30)
				ctx.translate(x, y)
				ctx.rotate(deg * Math.PI / 180)
				ctx.fillStyle = this.randomColor(this.colorMin, this.colorMax)
				ctx.fillText(txt, 0, 0)
				ctx.draw(true)

				ctx.restore() // 恢复之前状态
			},
			drawLine(ctx) {
				// 绘制干扰线
				for (let i = 0; i < 2; i++) {
					ctx.strokeStyle = this.randomColor(
						this.lineColorMin,
						this.lineColorMax
					)
					ctx.beginPath()
					ctx.moveTo(
						this.randomNum(0, this.contentWidth),
						this.randomNum(0, this.contentHeight)
					)
					ctx.lineTo(
						this.randomNum(0, this.contentWidth),
						this.randomNum(0, this.contentHeight)
					)
					ctx.stroke()
				}
			},
			drawDot(ctx) {
				// 绘制干扰点
				for (let i = 0; i < 20; i++) {
					ctx.fillStyle = this.randomColor(0, 255)
					ctx.beginPath()
					ctx.arc(
						this.randomNum(0, this.contentWidth),
						this.randomNum(0, this.contentHeight),
						1,
						0,
						2 * Math.PI
					)
					ctx.fill()
				}
			}
		},
		watch: {
			identifyCode() {
				this.drawPic()
			}
		},
		mounted() {
			this.$nextTick(() => {
				this.drawPic()
			})
		}
	}
</script>
<style scoped>
	.s-canvas {
		height: 38px;
		cursor: pointer;
	}

	.s-canvas canvas {
		margin-top: 1px;
		margin-left: 8px;
	}
</style>